Field of the Invention
The present invention relates to an image forming apparatus.
Description of the Related Art
Conventionally, an electrophotographic image forming apparatus is known such as a printer or a copying machine. Particularly, a so-called tandem color image forming apparatus is known in which a plurality of image carriers are disposed in a vertical direction to face one intermediate transfer belt and forming a full color image.
In such an image forming apparatus, an endless belt member, for example the intermediate transfer belt, is mounted, and the belt member is stretched around a plurality of rollers and rotationally operated. When the apparatus or the belt member is distorted, the belt member may meander and deviate during continuous rotational operation. The deviation of the belt member positionally shifts images transferred from the image carriers, and leads to deterioration in quality of the image. Therefore, in the image forming apparatus, steering control for correcting deviation of the belt member generated during performance of a job is performed in order to bring the belt member closer to a belt reference position.
For example, JP 2013-97141 A discloses an image forming apparatus which performs correction of meandering of an intermediate transfer belt corresponding to the steering control. In this image forming apparatus, when an operation command (job) is input, normal drive is started. During the normal drive, correction of meandering is performed using a first meandering correction mode. In the first meandering correction mode, a meandering correction unit is driven, based on a meandering direction and a meandering amount which are obtained by monitoring the intermediate transfer belt, and the intermediate transfer belt is returned to an appropriate position during rotational operation of the intermediate transfer belt. As a result of the meandering correction using the first meandering correction mode, when an edge position is less than a predetermined threshold, the process returns to the first meandering correction mode, and when the edge position is not less than the threshold, the meandering correction is performed by a maximum amount of correction.
However, in such an image forming apparatus, deviation of the belt member may be gradually accumulated, and even if the steering control is performed, large deviation may be generated in the belt member. For example, short-time jobs intermittently performed significantly bring about such a problem. Further, when the large deviation is generated, correction operation is performed by a large amount of control, in view of protection of the belt, as disclosed in JP 2013-97141 A. However, the correction operation is performed even during performance of the job, and thus, the correction operation results in the problem that the image quality is deteriorated and an output object is useless.